You won't regret it. It is, by and far, the best thing I have ever added to my boat.
While I have birds, I don't have networking birds(Helix 7's) The only features you lose are contour following and room to store more tracks and spot locks. I think you can store 6 of each on its own. Not sure.
Just being able to sit in a spot in just about any weather is worth the money, add the very easy steering and cruise control and it's easily worth the money.
I was using a FX 21 with a Fortex 112 on it Thursday night and the hole time I was wishing I had my little Nitro.....because the Ultrex makes my boat better for fishing VS a $60,000 boat without it.